The use of LED's (Light Emitting Diodes) for purposes of solid state lighting, and in particular illumination lighting, is gaining more and more interest. Applications where LED's could be used as a source of illumination lighting, and not just as an indicator lamp, include room lighting, and in particular shopping area lighting, road lighting and automotive lighting, and in particular in automotive headlight applications. Common for all these new applications is that a LED, or often an array of LED's provided on a chip, is operated at a high power to provide the desired light output. The high power also results in heat build up in the LED chip. Such heat build up decreases the efficiency in converting the electric power to light, i.e. decreases the lm/W value, and may also cause the destruction of the LED chip due to irreversible thermal damage. Some newer types of LED devices that are useful for this type of application include hybrid phosphor converted modules and colour mixing RG(A)B modules. Heat build up in the LED device will also lead to heat build up in the luminescent materials of e.g. hybrid phosphor converted modules. The efficiency of the phosphor materials drop as the temperature rises and thus the light output will be lower than desired. WO 03/096387 describes a high intensity light source comprising a micro array of LED's placed on a substrate. In one embodiment a light bar is provided in which modules comprising arrays of LED devices formed on conductive substrates are mounted. The light bar is provided with a fluid circulation channel that is supplied with a coolant. The coolant is circulated between upper and lower metal plates to cool those parts of the light bar housing that requires cooling.
A problem with the lighting arrangement of WO 03/096387 is that it is quite complicated and requires quite much space. This makes it expensive and less useful for applications where space is limited.